ESyS-Particle

normalK and shearK Parameters

Asked by Jeff Steadman

The NRotFrictionPrms interaction group has three parameters. A normalK, dynamicMu, and a shearK have to be defined for the interaction. In the tutorial it says that if the shear force in the springs exceeds the Normal Force*dynamicMu then, sliding will commence. This makes sense to me.

The normalK parameter is a parameter used for elastic replusion. Based on the normalK parameter, how do you determine when the particles will break apart. I noticed for the NRotBondPrms interaction group a break distance has to be specified as a parameter. If no break distance is defined in the interaction group then when do particles break apart and, how is the normalK parameter used in this calculations.

Thanks.

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Dion Weatherley (d-weatherley) said : 		#1

Hi Jeff,

NRotFrictionPrms is an unbonded interaction, similar to NRotElasticPrms. A non-zero (normal and shear) force is applied to the particle-pair only when the distance between the particles (dn) is less than the sum of the particle radii i.e. the particles are touching one-another. Should these two particles regain contact after moving apart, the frictional interaction is reset. Specifically, the net tangential displacement (ds) is reset to zero and frictional sliding will only recommence once shearK * ds > dynamicMu * normalK * dn

Cheers,

Dion

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Dion Weatherley (d-weatherley) said : 		#2

opps, that formula should have been:
shearK * ds > dynamiceMu * normalK * (dn - (R1 + R2))
where Ri is the radius of particle i=1,2 undergoing this interaction.

Cheers,

Dion.

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